Among the modern requirements of foundry binder systems, in particular for the cold-box, polyurethane no-bake and shell molding methods, besides reducing the nasal nuisance and the pollution emission, important features which need to be satisfied are to reduce the condensate formation (permanent mold casting in chimney region), to increase the thermal stability and to reduce the evolution of gases.
Foundry binder systems often contain phenolic resins. Phenolic resins are synthetic resins which are obtained by condensation of phenols and aldehydes and optionally by modifying the resulting condensates. Typical examples of such phenolic resins are novolacs, resols and benzyl ether resins (high-o,o′-resols). The latter are described for example in U.S. Pat. No. 3,495,797, and their use as resin components for foundry binders is described for example in U.S. Pat. No. 3,676,392 and U.S. Pat. No. 3,409,579. A detailed description of benzyl ether resins may be found in DE 10 2004 057 671 B4, paragraph [0004].
Modification of the properties of phenolic resins by reaction with silicon compounds has already been described in some documents.
U.S. Pat. No. 7,259,221 B2 describes the reaction of phenolic plastics with silanes, in particular with alkyltrialkoxysilanes. The use of the modified silanes in rubber mixtures is furthermore described. GB 746,498 describes the reaction of organosilanes with methylolphenol esters. EP 0 013 402 relates to siloxane-modified novolacs, which are produced by reacting novolacs with bifunctional polysiloxanes. US 2005/0284087 describes the reaction of a phenolic resin with an epoxysilane. EP 1 086 972 B1 describes the reaction of condensates of tetraalkyl orthosilicic acid esters with novolacs. U.S. Pat. No. 4,022,753 describes reaction products of polysiloxanes, which contain phenolic hydroxyl groups. GB 951,065 A describes the production of a condensation product starting from phenol-formaldehyde resols and alkoxyarylsilanes or alkoxyarylpolysiloxanes. EP 423 476 A2 describes the reaction of an alkoxysilane with a phenolic resin. JP 09-216937 describes a composition which contains silane-modified phenolic resins. U.S. Pat. No. 6,441,106 B1 describes the production of modified phenolic resins from phenolic resins and tetraalkoxysilanes and alkylalkoxysilanes. EP 0 423 476 A2 describes the production of modified phenolic resins from phenolic resins and monoalkyltrialkoxysilanes. The use of such modified phenolic resins as a binder or a constituent of a binder in order to form foundry molding materials is described neither in U.S. Pat. No. 6,441,106 B1 nor in EP 0 423 476 2. U.S. Pat. No. 3,409,579 describes binders for foundry technology. Alkoxysilanes are described therein as additives which improve the adhesion and are used in an amount of from 0.1 to 2 wt. %.